全谱段高光谱成像仪光学系统设计

Optical System Design of Full-Spectrum Hyperspectral Imaging Spectrometer

为满足全谱段高光谱成像探测一体化应用需求,开展了可见至长波红外(LWIR)共口径成像光谱仪光学设计。前置像方远心物镜采用离轴三反结构实现,利用视场分离分光和分色片分光相结合的方法实现了可见至LWIR的四谱段划分。后置光谱仪采用非对称式凸面光栅Offner结构,将中波红外(MWIR)与LWIR光谱仪的放大率设置为0.90和0.61,以满足设计指标和成像质量的要求。设计和分析结果表明:所提系统在600 km轨道高度处的幅宽为30 km;可见至短波红外(SWIR)的F数为2.6,可见/近红外(VNIR)光谱分辨率和SWIR光谱分辨率分别优于5 nm和10 nm,像元分辨率为30 m;MWIR谱段和LWIR谱段的F数分别达到2.3和1.5,光谱分辨率分别优于50 nm和100 nm,像元分辨率分别为50 m和74 m;各谱段在Nyquist频率处的调制传递函数(MTF)均接近衍射极限,谱线弯曲和色畸变均小于探测器像元尺寸的1/10。

In order to meet the integrated application requirements of full-spectrum hyperspectral imaging and detection,this paper designs a visible-to-long-wave infrared(LWIR)co-aperture imaging spectrometer.The front image square telecentric objective is realized by an off-axis three-mirror structure,and the spectrum is divided into four segments by the field of view separation and beam splitter.The post spectrometer adopts an Offner structure with asymmetric convex grating,and the magnifications of the middle-wave infrared(MWIR)and LWIR spectrometers are set to 0.90 and 0.61,so as to meet the requirements of design specification and imaging quality.The design and analysis results show that the proposed system achieves a ground coverage width of 30 km at an orbital height of 600 km.The F number of visible spectral band to short-wave infrared(SWIR)spectral band is 2.6,and resolutions of visible/near infrared(VNIR)and SWIR are better than 5 nm and 10 nm,respectively,with a pixel resolution of 30 m.The F number of the MWIR and LWIR spectral bands is 2.3 and 1.5,respectively,and their spectral resolutions are better than 50 nm and 100 nm,with a pixel resolution of 50 m and 74 m.The modulation transfer function(MTF)of each spectral band is close to the diffraction limit at the Nyquist frequency,and the spectral line curvature and color distortion are less than 1/10 of the detector′s pixel size.